Controllable stop fob regulating



2 SHEET-SHEET 2 IOI E. H. FLETCHER CONTROLLABLE STOP FOR REGULATING STROKES FIG. 3

OF FLUID PRESSURE APPARATUS Original Filed May 11. 1949 IOO J H: I03 I04 Aug. 26, 1952 F IG. 4

FIG. 5

ATTORNEY I03 ,/&\\\

Reissued Aug. 26, 1952 CONTROLLABLE STOP FOB REGULATING STROKES OF FLUID PRESSURE APPA- RATUS Edward H. Fletcher. Waterloo, Iowa, assignor to Deere Manufacturing Co., Dubuque, Iowa, a

corporation oi Iowa Original No. 2,545,573, dated March 20, 1951, Se-

rial No. 92,558, May 11 1949. Application for reissue March 17, 1952, SerialNo. 276,942

' Claims. (Cl. 121-38) Matter enclosed in heavy brackets II appears in the original-patent but forms no part of this reissue specification: matter printed in italics indicates the additions made by reissue.

This invention relates to fluid-pressure apparatus and particularly to means for regulating or controlling the stroke of a fluid-pressure motor.

Although the principles of the invention are capable of application in many and divers fields. the preferred form of the invention to be detailed subsequently herein was designed primarily for utilization in the regulation or control of agricultural implements of that class comprising a vehicle or equivalent supporting frame having a source of power for driving a fluid-pressure pump or the like to supply fluid under pressure to a motor, such as a cylinder and piston assembly, which is in turn connected to an adjustable implement part, such as a plow or earth-working tool or the platform of a harvester or equivalent machine. In the case of a plow, for example, it is desirable to adjust the plow so that it will plow at a uniform depth. It is further desirable that the plow may be raised from its plowing or working position, as at the end of a furrow, and be readily returned to working position by lowering of the same to the selected uniform depth, as when beginninga new furrow.

In one particular system, this general result is efiiciently and simply achieved by the use of a pair of cooperating stops or abutment members on the relatively movable motor parts, such as the cylinder and piston. The fluid-pressure system is provided with a relief valve which operates in response to an excess of pressure in the system to return a main control valve to neutral to discontinue the supply of fluid to the motor or the exhaust of fluid from the motor. These cooperating stops may be adjusted in accordance with the desired position of adjustment of the implement part, so that when the implement part reaches its desired position, one stop will engage the other and prevent further relative movement of the motor parts, bringing about a condition of excess pressure which will affect the main control valve to isolate the motor from the fluidpressure source. A disadvantage noted in this system is that the stops are positive in action and the motor cannot be operated to adjust the implement part beyond the position selected; that is to say, the plow, for example, having once had its position determined by the cooperating stops, cannot be moved to a greater depth without a readjustment of the stops. In the case of a plow or analogous equipment, the implement part or equivalent adjustable part is remotely located with respect to the fluid-pressure source, since the latter is on the tractor or propelling vehicle and the adjustable part is connected behind the 2 tractor, for example, on trailing supporting structure. Therefore, it is necessary in the system referred to above for the operator to dismount from the tractor to accomplish a readjuistment' of the cooperating stops.

According to the present invention, the above system is modified and improved to the extent that stop means is eflective to accomplish a limit on the amount of relative movement of the motor part for the general purposes stated above. The cooperating parts of the stop means are ad- Justable so that any desired normal limit may be effected. However, the stop means further includes provision for additional movement beyond the range 01' movement of the motor parts determined by the original setting 01' the stops. This object is preferably achieved in a system in which the fluid-pressure apparatus has a main control valve capable of regulating the volume of fluid supplied to the motor so that the motor may be caused to operate at either a high or a low speed. The control valve has, of course, a neutral position in which the motor is isolated from the fluidpressure source. The system further preferably includes a pressure-relief valve effective to return the control valve to its neutral position in response to any condition of excess pressure in the system. In operation, the stop means is set in a desired position of adjustment and the normal adjusted position of the implement is effected after predetermined relative movement of the motor parts, the system operating like that previously described to the extent that a condition of excess pressure is created to cause the main control valve to return to neutral. In the present case, however, should the operator desire to move the implement beyond its normal adjusted position, he may operate the system at low speed, an important feature of the invention residing in the provision of a valve in the stop means which has a throttling or by-pass means which establishes a restriction to operation 01' the system at high speed but which will permit operation of the system at low speed.

An important object of the invention is to adapt the general idea discussed above to a fluid-presby the present invention will become apparent to those versed'in the art as a preferred form of the invention is fully described and illustrated in the following detailed description and accompanying sheets of drawings in which: a

Figure 1 is a representative illustration of, an implement arrangement to which the improved system may be applied;

Figure 2 is an enlarged sectional view, somewhat schematic, of that portion of the fluid-pressure apparatus including the source of fluid pressure, the pressure-relief valve. and the main control valve;

Figure 3 is an enlarged side elevational view. partly in section, of the fluid-pressure motor as incorporating the improved stop means; and

Figures4,5and6areenlargedfragmentary sectional views showing different operating positions of the valve and control members.

The representative structure chosen for the purposes of illustration comprises. as shown in Figure l, a tractor and a trailing implement. The tractor may be of any conventional construction and includes a longitudinal main body ll carried on rear traction wheels II. and provided with a rearwardiy disposed operator's station If ahead of which is located an engine hoodstructure it within which is enclosed the usual power plant (not shown) for supplying power to the traction wheels II.

The particular implement shown by way of iilustration is a plow having a main frame ll provided with a cranked axle I! on which is Journaled a ground wheel it. The forward end of the frame it includes a draft member II which is pivotally connected at II to a conventional drawbar II on the tractor body II. The groundworking tool is here represented by a plow bottom fl.

The plow frame or supporting structure I4 is provided Just above the wheel II with a bearing 1 .1 in substantially their uppermost positions.

Rocking of the bell crank in a counterclockwise direction will result in a lowering of the parts It and II. It will be understood that the connection of the hitch H to the frame it is accomplished in such manner as to provide for the necessary articulation of the frame I I with respect to the hitch member l1, as by a pivot at 15. The general structure and arrangement of the tractor and implement are or may be conventional and resort need not be had to further detailed description thereof.

Adjustment of the plow bottom 2. between its raised position as shown and a lowered or ground-working position is accomplished by fluid-pressure apparatus comprising a fluid motor fl; means for controlling the supply of fluid under pressure to the motor. designated generally by the numeral 21 in Figure l; and a fluidpressure circuit including the components ll and 21 and a pair of conduits 2| and II.

The motor 28 comprises a cylinder ll and a piston ll slidable therein (Figure 3). The cylinder Ill forms a chamber within which the piston Si is reciprocable and the latter includes a 4 piston rod 32 which is provided at its free end with a clevis I for attachment at N to the upper end of the-bell crank arm 23. The closed end of the cylinder 30 is provided with a clevis 8| which is connected at It to an upturned supporting portion 31 at the forward end of the implement frame ll. It will be seen that extension of the piston and piston rod with respect to the cylinder II will rock the bell crank 22-23 in a clockwise direction to raise the plow bottom and frame. and that retraction of these piston and piston rod will rock the bell crankln a counterclockwise direction to lower the plow botand frame.

The controlling and supplying means 21 is shown in Figure 2 as em o y n typical construction in which the working parts are contained in a suitable housing 3| which maybe secured to the rear portion of the tractor body II in any appropriate manner. The housing is provided with a vertical valve cylinder 3! within which a valve piston ll is axially shiftable. The housing is provided with a fluid-supply or highpressure passage or conduit ll which is connected at one end to a suitable source of supply.

such as a pump 42 (illustrated schematically in the pump is connected as by an intake conduit 46. The reservoir II is connected by a return conduit 45 to an exhaust passage 40 in the housing 38. The passage it includes a pair of branches 41 and II which are connected at axially spaced points in communication with the valve cylinder ll. The fluid-pressure-transmitting conduits ll and 2! are also connected to the valve cylinder 38 by means of a pair of passages or conduits ll and ill, respectively. A springloaded check valve ii is provided in the passage 45-" and a similar check valve 52 is provided in the passage. 1-28.

The valve. shown in Figure 2 in its neutral position and both check valves ii and II are closed; therefore, the fluid motor It is hydraulically locked and the implement part "-2! will be maintained in its selected position. Regulation of the control valve 40 is effected by means of a control lever 53 carried by the housing 30 on a transverse rockshait 54 and conveniently located with respect to the operators station I! (Figure l) Within the housing II, the rockshaft Bl has'flxed thereto a crank arm it which is connected by a link it to the upper end of the valve 4|. It will be evident thatrocking of the control lever II in one direction or the other will result in axial shifting of the valv III in the valve cylinder 38.

The valve 40. as illustrated. is of the spool type and is so constructed that in its neutral position. as shown, fluid supplied by the pump 42 through the passage ll will circulate axially in opposite directions from the central portion of the valve cylinder I! to end portions of the cylinder I! for return through the exhaust branches l1 and 4! and thence through the exhaust passage It and return duct I! to the reservoir 43. It will be understood, of course. that the pump 42 is operated by any suitable means on the tractor.

For the purposes of eflecting the desired control of the fluid-pressure system, the valve 4| includes a central cylindrical portion 51, and upper and lower cylindrical portions it and 59 respectively. Intermediate the portions 51 and II. the valve 40 is provided with a tapered section I0, and a similar tapered section II is provided intermediate the portions 51 and N. The valve cylinder 3! is of substantially uniform diameter throughout its length except for annular recesses I2, ll and N. These recesses correspond in position respectively with the high-pressure passage 4| and exhaust branches 41 and 4B. In the neutral position of the valve 40, as shown in Figure 2, the tapered portions 60 and ii are located as illustrated with respect to the check valves 51 and 62, respectively.

Operation of the system to the extent described is as follows: The control lever 53 may be moved a maximum distance forwardly, or in a counterclockwise direction, to eiiect maximum upward shitting oi the valve 40 in the valve cylinder 8!. The result is that the cylindrical portion 51 of the valve cuts ofi the supply or fluid upwardly through the valve cylinder and directs the fluid downwardly to the check valve 52. The pressure rise in this portion of the system causes the check valve 52 to open to its maximum extent and fluid is supplied under pressure through the passage M to the lower conduit 29 which, in turn, supplies fluid under pressure to the closed end or the cylinder through a conduit or passage Ii. Ignoring for the moment the detailed structure of the cylinder 30, it will be seen that the result is to extend the piston rod 32 with respect to the cylinder and thus to raise the implement to the position shown in Figure l.

Simultaneously with the raising of the valve 40, as aforesaid, the tapered portion 80 engages the stem of the upper check valve ii and causes this valve to open to its maximum extent against its loading spring, thereby establishing communication between the upper conduit 28 and upper passage 49 and providing for the exhaust of fluid at its maximum rate of flow from the rod end of the cylinder past the upper portion of the valve 40 and into the exhaust branch 41 and thence through the passages 48 and 45 to the reservoir 43. Return of the control lever 63 to its neutral position eifects hydraulic locking of the motor 28 as stated above.

The conduit 28 is connected to the rod end of the cylinder 30 by means of a passage 66 and intersecting bore 61, the latter including a generally circular port I'l all or which are formed in a casting 30 which provides, in eflect, part of the cylinder 30. The control of the port i1 will be described below.

Rocking or the lever 53 a maximum distance in a clockwise direction, or to the rear, as viewed in Figure l, reverses the procedure just described and the motor 28 may be contracted to effect lowering of the implement part.

The control means 21 presently illustrated includes means for controlling the volume of fluid under pressure to the motor 28 to eil'ect either high-speed or low-speed operation or the motor. This means includes the valve 46 and the parts just described, together with means for indicating to the operator certain positions of the valve in which the system may be caused to operate at either of the speeds referred to. For this purpose. the control lever rockshaft 54 carries flxedly thereon within the housing 38 a plate 10 which is centrally notched at H to normally receive a roller 12 which forms part of a' spring-loaded arm II that is pivoted to an interior portion of the housing 38, as at H. Opposite portions of the plate member Hi that border the notch Ii are substantially straight but terminate in lugs shifting of the valve 40 results in only partial opening or cracking of the valve ll, thus metering, or reducing the rate of flow of. fluid exhausted from the motor through the conduit 28. Although the pressure in the system will actually open the lower valve 52 to its maximum, metering as aforesaid at the valve 5| will result in diver sion of part of the fluid on the highside back to the reservoir through the pressure-relief means described below. Various types of metering valves may be used in place or the check valves II and.

52, as in assignee's co-pending application, Serial No. 628,626, filed November 5, 1945, now Patent No, 2,532,552, granted December 5, 1950, but, since the present system is shown only diagrammatically, the detailed structure has been omitted.

In the event that the operator desires to efiect a relatively fine adjustment of his implement, he will utilize this slow speed. He can, of course, move the control lever past the point at which he feels engagement between the roller 12 and lug 15 to obtain high-speed operation. A similar result may be obtanied in movement of the lever 53 in the opposite direction.

The control system illustrated has means for automatically returning the control valve I to neutral in response to excess pressure in the system. Part of this means includes an arm 11 fixed to the rockshaft 54 and associated with a bell crank having arms 18 and 15. This bell crank is pivoted at an to the interior of the housing 38. The arm 18 carries a roller Bl which rides on an arcuate portion 82 of the arm ll. This portion is formed about the axis of the rockshait 54 and terminates at each of its opposite ends in cut-oft corners 83 and 84 respectively. The bell crank 18-19 is spring-loaded by means including a rod 85, a compression spring 88, and a washer 81. A portion of the housing 38 is bored at B8 to accommodate the spring 88. The rod 85 is connected at one end to the arm 19 and is headed at its other end to carry the washer 81. The spring 86 is confined between the washer l1 and a wall 88 which forms the end of the bore 38. The action of the spring is such as to keep the roller Si in constant engagement with the arcuate portion 82 or either of the comers I3 and N, as the case may be.

The extent of the are 82 is proportional to the range of movement of the control lever 53 in efiecting slow-speed operation of the system in either direction. Hence, when the operator releases the ccntrol lever 53 the spring-loaded lever or arm 13 will be effective to return it to neutral from either of its slow-speed positions, inasmuch as the corners 83 and B4 on the plate 11 do not, in this range of movement of the lever 53, cooperate with the roller 8| to establish a look on the rockshaft 5|. Also, operation of the relief valve as an adjunct to metering, as stated above, will not ailect the control lever. since the lever is not locked in either slow-speed position. However, when the control lever is moved to its maximum or high-speed position in either direction,

7 the roller it engages with one or the other of the corners 83 or 84 and acts to hold the control lever It in either maximum position. The operator may, 01' course, overcome the locking action at will and move the control lever II to any other position.

The housing 38 has a bore 90 below the bore 88, these bores opening to the return passage 48. A

rests on an annular apertured wall 9! which separates the bore 90 from a coaxial bore 93. Communication between the passage ti and the bore 93 is controlled by a relief valve 94, normally held on a valve seat 95 by means of a relatively heavy compression spring 98. The spring 98 is calibrated to hold the valve 84 seated during operation of the system at normal pressures.

In the event abnormal rise of pressure in the system, the valve 94 will open against the spring 86 and fluid from the high-pressure passage ll will enter the bore 93, pass through the apertured wall 92 and raise the valve member 9| in the bore 90. Upward movement of the valve member 9i is followed by engagement oi this valve member with the headed end or the rod ill, thus compressing the spring 88 and rocking the bell crank l819 in a counterclockwise direction to release the roller Bl from one or the other of the corners 83 or ill on the plate 11. Upon release of the roller from the plate, the springloaded arm or lever 13 causes the rockshai't 54 and plate It to move angularly until the roller 12 again seats in the arcuate notch H, which position determines the neutral position of the valve 40. Pressure reliei valves of this type and tor the purpose described are well known and any conventional construction may be substituted for that illustrated. Excess fluid pressure that causes upward movement of the valve member SI and unlocking oi the bell crank |Bll is returned to the reservoir through the passages 45 and It by means of a pair of intersecting bores 91 and 98 in the valve member 8|. It will be understood, 0! course, that when the valve member 0| raises, the bore 88 will communicate with the horizontal portion of the return conduit 46.

In systems oi the type heretofore known, an excellent example of which is disclosed and claimed in the U. S. Patent 2,442,306, issued to McCormick, the pressure-relief means is utilized in connection with adjustable stop means between the piston and piston rod for deliberately creating a condition in which part of the stop means may interengage at a selected point to limit travel of the piston rod with respect to the cylinder, thereby causing the pressure-relief means to return the control valve to neutral. Such arrangement, as aforesaid, is desirable in returninga plow, for example, to working position after it has been raised. In the use of a system or the type rei'erred to, the operator is relieved of the burden of re-determining the ground-working position of his implement upon lowering oi the im plement from a raised position. These characteristics are, of course, present in other situations, as in a harvester, for example, in connection with the raising and lowering of the harvester platform; although, the operations may be in reverse order.

One characteristic of the system described generally above is that the stops are positive; that is, once set, the stops must be readjusted manually in the event that the operator desires to adjust the implement to a position of increased depth, for example, beyond that determined by valve BI is slidable in the bore 90 and normally the stops. Then, he must again readjust the stops to secure his original adjustment, all of which requires that the operator dismount from the tractor and make the necessary adjustment. According to the present invention. there is provided stop means including provision whereby the stops or their equivalent may be controlled by the operator through the medium of the control lever II; therefore, the operator need not dismount from the tractor. At the same time, the stop means is so arranged as to retain the original adjustment even though allowing for variations in this adjustment from time to time. The manner in which these desirable results are achieved in the preferred form of the invention illustrated will be described below.

As previously described, the operator may. by means of the lever 53. rock the rockshait 54 so that the valve 40 is moved upwardly in the valve cylinder 39, resulting in the transmission of fluid under pressure through the conduit 28 to the closed or left-hand end of the cylinder 30 and simultaneously opening the check valve II for the return or exhaust oi fluid through the conduit 28 to the reservoir 43 via the passages ll, 41, 46 and 4!.

The port 61* and passage 68 are under control of a valve HID. This valve, like the port 61', is generally circular and the outside diameter or the valve is somewhat less than the I inside diameter of the port so that a slight leakage clearance is provided. In the preferred form of the invention illustrated, the valve Hill is guided in its movement by means including a control member or rod III which is axially slidably carried by the casing part coaxially with the port 61' and valve Hill, the casing part being provided with a bore I02 for this purpose. The valve I" i centrally apertured at I03 and the rod llll extends slidably therethrough. The inner end 01 the rod lfll, or that portion thereoi approximate to th port 61-, is provided with a portion in the form 01 an enlarged head I. The rod is substantially elongated and projects outside the casing part 30', for a purpose to presently appear. A plate I05 is carried at the end of the casing part Ill, and is apertured respectively at I08 and ID! to accommodate the rod lfll and the piston rod 32. An appropriate fluid-pressure seal I01 is associated with the rod III and the casing part 30 for obvious \ifl'. The port 61* includes means, here prelerably in the form 01' a circular snap ring Iill, for limiting or restraining movement or the valve I00 beyond its port-restricting position, as best shown in iiigures 5 and 6. The outside diameter of the rod lill is somewhat less than the inside diameter of the central aperture in the valve I" through which. ;,the rod passes, thereby providing a slight leakage clearance for fluid under pressure. j

The portion of the rodljtl,l that extends outside the motor 'comprises*-o ne of a pair of cooperative elements for controlling the valve I", the other 01' which is in the form of a stop on the piston rod 32. In the presentinstance,

the form of stop illustrated is a bent member III, preferably formed of spring steel, and apertured to receive the piston rod 32. The free ends of the member Ill may be squeezed together manually so that the position of the member III may be adjusted on the rod 02, thereby giving the user a variety of ranges through which the piston will move before the member III-engages the rod IOI.

Operation When fluid under pressure is supplied through the conduit 29 and passage 65 to the closed end of the cylinder 10, the piston Si is caused to move to the right, thus extending the distance between the points It and I6 and effecting raising of the plow "-20. At the same time, the chamber formed between the casing part and the right-hand side of the piston 3| is reduced and fluid is exhausted through the port 01" and passage 66 to the chamber 20, ultimately to return to the reservoir as previously described. Fluid exhausted through the port 61' by reduction in the cylinder chamber just described is applied to the radial fluid-pressure-receivable area at the port side of the valve I00, with the result that the valve is shifted to the right.

against the light compression spring I09. The inner end portion or head I04 on the rod IOI likewise constitutes a radial fluid-pressure-recelvable area which is also subject to exhaust fluid pressure through the port 61, with the result that the rod IN is ultimately shifted by exhaust fluid pressure to the right. However, in a previous retraction stroke of the motor 26, wherein the piston II moves to the left, the stop member III will have engaged the rod IOI to move it to the position illustrated in Figure 5, for example. In this case, initial application of fluid pressure at the left-hand side of the piston M will result in relatively lowspeed operation of the piston 3| to the right, because of the restriction set up by the closed valve I00. However, as the piston 3| moves slightly to the right, it releases the member III from the rod IOI until the restriction at the port 01 ultimately builds up pressure sufllciently to effect opening of the valve I00 even though the rod IN is forcibly held by the member III. The slight leakage through the port 61 has now become a relatively considerable volume of fluid and the piston 3| may be moved more rapidly to the right. Ultimately, exhaust fluid pressure shifts the rod IN to its maximum position to the right.

Ordinarily, the operator will extend the motor 20 to its maximum distance to effect maximum lifting of the plow. The rod IOI extends only a limited distance outside the casing part 30" and, depending upon the adjustment of the member III. the member III normally will be relatively widely separated from the rod II. it being understood that the position of the member III on the piston rod 32 ultimately determines the position at which the plow will stop when lowered; although, as will be presently described, this selected lowered position of the plow may be exceeded if desired.

Assuming now that the operator has kept the stop III at a desired position on the piston rod 02, he may rock the control lever 53 in a clockwise direction (as viewed in Figures 1 and 2) to efl'ect downward movement of the control valve 40. This will result in mechanically opening the lower check valve 52 in the casing 30 so that free fluid communication is established between the conduit 20 and the reservoir. Simultaneously. the pressure rise in that portion of the valve cylinder above the valve portion 01 causes opening of the check valve II and transmission of fluid through the conduit 20 to the passage 00 and port 61'. Fluid is thus exhausted from the left-hand end of the cylinder through the conduit 20 and fluid under pressure is supplied to the right-hand end of the cylinder. Thus the chamber at the right-hand side of the piston is expanded; and, as the piston 32 moves to the left, the stop III gradually approaches the rod IOI. Although the spring I09 is sufliciently strong to cause closing of the valve I00 by itself, it does not have sufllcient strength to move both the valve I00 and the rod IOI, partly because of the additional fluid-pressurerecelvable area provided by the head I04 on the rod MI and partly because of friction occasioned by the fluid seal I01 on the rod IOI. Hence, the rod IOI, when positioned to the right, as illustrated in Figure 4, provides means for incurring or holding the port-opening position of the valve.

When the member III on the piston rod 02 engages the outer end of the rod Ni, ii; forcibly moves the rod IOI inwardly toward the port 01. This overcomes any fluid pressure on the rod and also overcomes any friction at the seal I01. Thereupon, the spring I09 is called upon merely to move the valve I00. Hence, the valve I00 follows the head and rod IOI to the left. As the valve IOI approaches the port 61. it establishes a restriction in the passage that communicates to the right-hand end of the cylinder and when the valve ultimately seats in the port 61* the restriction is so great as to cause a pressure rise in. the system. This pressure is greater than the maximum allowable, with the result that the pressure relief valve 94 is caused to operate and in turn effect movement of the control lever 53 to neutral position. This result follows, assuming that the operator has moved the control lever to its lower" position and has then released it. After the control lever 03 and valve 40 move to their neutral positions, as illustrated in Figure 2, the motor 20 is hydraulically locked and the pump 42 circulates fluid through the casing 08 at no appreciable pressure. Hence, closing of the valve I 00 in the port 0!- establishes a stop which limits lowering of the plow "-20. It will be understood. of course, that this result will obtain in connection with the determining of a particular position in any implement equipped with the invention here disclosed.

Now, if for some reason or other, the operator wishes to move the implement (here the plow) beyond its position as determined or selected by the valve I00 and control rod IOI, he may again move the control lever 50 so as to shift the valve 40 to its lower position. Although the restriction set up by the valve I00 in the port 01 will, as previously described, set up a condition causing excessive pressure in the system, the maximum pressure is still available in the passage 06. The operator may, by forcibly holding the control lever 53, maintain the lower position of the valve 40. Inasmuch as there is a slight leakage at the closed valve I00, both at the outside diameter of the valve and at the inside diameter of the aperture in the valve, fluid may be introduced to the right-hand end of the cylinder to cause further movement of the piston II to the sass? Cl and port I1. and further movement of the piston rod 32 and member III will move the rod Ill forcibly to the left beyond the position established by the valve. This overshifting of the is stopped or rod IN is permitted because of the one-way connection or engagement between the head ill of the rod ill and the valve ill. That is to say, the arrangement is such that movement of the rod to the right will carry with it the valve ill. Yet, movement of the rod IM to the left, beyond the position illustrated in Figure 5, will be separate from the valve I. Also, as previously described, the valve I may move to the right separate from the'rod lill.

Assuming now that the control by the operator is such as to achieve the position of the parts illustrated in Figure 6, the operator has only to release the lever 53 and the excess pressure built up in the system will again return the control valve to neutral. When the operator desires to again effect raising of the implement by extension of the motor 28, he has only to Summary It will be seen from the foregoing description and accompanying illustration that an improved and flexible form of control has been provided for a fluid-pressure system. particularly of the type illustrated, wherein selected or determined positions of implements are normally desired but wherein other positions may become necessary from time to time. These other positions may be achieved without rearranging mechanical connections, such as were heretofore known in the art.

Other features of the invention, not specifically pointed out above, will undoubtedly occur to those versed in the art. as likewise will numerous modifications and alterations in the preferred form of the invention illustrated, all of which may be'achieved without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is: I

1. In a fluid-pressure system: means providing a passage and a communicating, generally circular port for transmitting fluid under pressure at times in one direction and at times in the reverse direction: a generally circular valve selectively shiftable back and forth on the axis of the port between a port-opening position and a portclosing position, said valve and port being so formed as to provide for restricted passage of fluid when the valve is in port-closing position, and said valve having an area subject to reverse fiuid pressure for shifting of the valve to port-opening position; yielding means normally effective to incur the port-closing position of the valve; means for restraining the valve against overshifting beyond its port-closing position;

' means providing an axial aperture in the valve;

l2 valve aperture and having at the'port side of the valve a first portion providing an area subloct to reversed fluid pressure for axial shifting of the member in one direction corresponding to shifting of the valve to its port-opening position and 'a second portion at the other side of the valve providing for forcible axial shifting of the memher in the opposite direction; said port and said first portion of the member being so dimensioned that said first portion may enter the port when forcibly overshifted in said opposite direction while the valve is restrained at its port-closing position; and means-on the member providing for one-way engagement of the valve by the member when the member is shifted by reverse fluid pressure so that the valve is held by the member at port-opening position and so that the member may be overshifted as aforesaid.

2. In a fluid-pressure system: means providing a passage including a communicating port for transmitting fluid under pressure at times in one direction and at times in the reverse direction; a valve selectively shiftable back and forth between a port-opening position and a port closing position, said valve and port being so formed as to provide for restricted passage of fluid when the valve is in port-closing position, and said valve having an area subject to reverse fluid pressure for shifting of the valve to port-opening position; yielding means normally elfective to incur the port-closing position of the valve; means for restraining the valve against overshifting beyond its port-closing position; a control member shiftable relative to and extending at opposite sides of the valve, said member having at one side of the valve a first portion providing an area subject to reversed fluid pressure for shifting of the member in one direction corresponding to shifting of the valve to its portopening position and a second portion at the other side of the valve providing for forcible shifting of the member in the opposite direction; said passage and said first portion of the member being so dimensioned that said first portion may enter the port when forcibly overshifted in said opposite direction while the valve is restrained at its port-closing position; and means on the member providing for one-way engagement of the valve by the member when the member is shifted by reverse fluid pressure so that the valve is held by the member at port-opening position and so that the member may be overshifted as aforesaid.

3. In a fiuid-pressure system: means providing a passage for transmitting fluid at times in one direction and at times in the reverse direction; a valve shiftable selectively back and forth between a e-opening position and a passage-restricting position and having a fluid-pressure-receivable area subject to reversed fluid pressure for shifting of the valve to eopening position; a control member shiftable back and forth and having a first portion providing a fiuid-pressure-receivable area, subject to reversed fiuid pressure for shifting of the member in one direction toward a first position, and a second portion providing for forcible shifting of the member in the opposite-direction toward a second position; means for restraining the valve against overshifting beyond its passage restricting condition; means engageabie between the valve and the member for holding the valve in v e-opening position when the member is in its first position, said means being separable a control member extending slidably through the 'll to provide for forcible overshifting of the member restricting i 13 toward its second position and relative to the valve when the valve is restrained at its passage- I position; and means for incurring shiftingof the valve toward its passage-restricting position upon forcible shifting of the member toward its second position, and providing further for shifting of the valve toward passageopenlng position by reversed fluid pressure even though the member is forcibly held toward its second position.

4. In a cylinder and piston assembly in which the cylinder has an end wall and the piston has a piston rod extending outwardly through said wall, the improvement comprising: means providing a fluid passage in the end wall, including a bore paralleling the piston rod and opening as a coaxial circular port to the interior of the cylinder for carrying fluid to and from the cylinder; means in the end wall providing a smaller counterbore forming a shoulder at its Junction with the bore and spaced coaxially outwardly from the port, said counterbore opening through the end wall in the direction of outward extension of the piston rod; a control member slidable in the counterbore and having one end portion outside the end wall and another end within the bore having a circular head larger than the counterbore but smaller than the port; a circular, centrally apertured valve slidable on the member intermediate the head and the aforesaid shoulder and cooperative to seat in and be unseated from the port: biasing means interposed between the valve and said shoulder for urging the valve against the head and inwardly toward the port; means at the port for limiting inward movement of the valve but disposed out of the path of inv ward movement of the head; and means positionable on the piston rod outside the cylinder for engaging the member to move the member inwardly.

5. In a cylinder and piston assembly in which the cylinder has an end wall and the piston has a piston rod extending outwardly through said wall, the improvement comprising: means providing a fluid passage in the end wall, including a passage portion transverse to the piston rod and further including a bore generally parallel to the piston rod and intersecting said passage portion, said bore opening to the cylinder as a port for carrying fluid to and from the cylinder; means in the end wall providing a smaller counterbore forming a shoulder at its junction with the bore and spaced coaxlally outwardly from the port, said counterbore opening through the end wall in the direction of outward extension of the piston rod; a control member slidable in the counterbore and having one end portion outside the end wall and another end within the bore having a circular head largervthan the counterbore but smaller than the port; a circular, centrally apertured valve slidable on the member intermediate the head and the aforesaid shoulder and cooperative to seat in and be unseated from the port; biasing means interposed between the valve and said shoulder for urging the valve against the head and inwardly toward the port; means at the port for limiting inward movement of the valve but disposed out of the path oi inward movement of the head; and means positionable on the piston rod outside the cylinder for engaging the member to move the member inwardly.

6. In a fluid pressure system, the combination of: a fluid motor having first and second relatively movable motor parts, the flrst of which in- 14 eludes a fluid-receiving chamber and means providinga passage and a communicating. generally circular port for transmitting fluid under pressure at times in one direction to and at times in the reverse direction from said chamber; a generally circular valve selectively shiftable back and forth on the axis of the port between a portopening position and a port-closing position. said valve and port being so formed that they provide for-restricted passage of fluid when the valve is in port-closing position. and said valve having an area subject to reverse fluid pressure for shifting of the valve to port-opening position; yielding means normally effective to incur the portclosing position of the valve: means for restraining the valve against over-shifting beyond its port-closing position; means providing an axial aperture in the valve; a control member extending slidably through the valve aperture and having at the port side of the valve a first portion providing an area subject to reverse fluid pressure for axial shifting of the member in one direction corresponding to shifting of the valve to its port-opening position and a second portion at the other side of the valve arranged to be engaged by the second motor part upon predetermined shifting of said second motor part for forcible axial shifting of the member in the opposite direction, said port and said flrst portion of the member being so dimensioned that said flrst portion may enter the port when forcibly overshifted in said opposite direction while the valve is restrained in its port-closing position; and means on the member providing for one-way engagement of the valve by the member when the member is shifted by reverse fluid pressure so that the valve is held by the member at portopening position and so that the member may be over-shifted as aforesaid.

'7. In a fluid pressure system. the combination of: a fluid motor having flrst and second relatively movable motor parts, the flrst of which includes a fluid-receiving chamber and means. providing a passage including communicating ports for transmitting fluid under pressure at times in one direction to and at times in the reverse direction from said chamber; a valve selectively shiftable back and forth between a port-opening position and a port-closing position, said valve and port being so formed as to provide for restricted passage of fluid when the valve is in portclosing position, and said valve having an area subject to reverse fluid pressure for shifting of the valve to port-opening position; yielding means normally effective to ,incur the port-closing position of the valve; means for restraining the valve against over-shifting beyond its port-closing position; a control member shiftable relative to and extending at opposite sides of the valve, said member having at one side of the valve a flrst portion providing an area subject to reversed fluid pressure for shifting of the member in one direction corresponding to shifting of the valve to its port-opening position and a second portion at the other side of the valve and engageable by said second motor part upon predetermined movement of said second motor part relative to the flrst motor part and providing for forcible shifting of the member in the opposite direction; said passage and said first portion of the member being so dimensioned that said flrst portion may enter the port when forcibly over-shifted in said opposite direction while the valve is restrained at its port-closing position; and means on the member providing for one-way engagement of the 

